Abstract 5551: Double Deficiency of Tumor Necrosis Factor-α and Interferon-γ in Bone Marrow-Derived Cells Prevents Neointimal Formation in a Murine Model of Vascular Injury

Neointimal formation after percutaneous coronary intervention (PCI), termed restenosis, limits therapeutic revascularization. Recent evidence indicates that inflammatory responses induced by inflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ), are involved in the progression of neointimal formation. However, the role of TNF-α and IFN-γ in the restenosis after PCI has not been fully understood. The purpose of this study is to examine the impact of TNF-α and IFN-γ in bone marrow-derived cells in the development of neointimal formation after vascular injury in mice. Wild-type (WT), TNF-α-deficient (TNF-α −/− ), IFN-γ-deficient (IFN-γ −/− ), and TNF-α/IFN-γ double-deficient (DKO) mice were subjected to wire-mediated vascular injury of the right femoral artery. Immunohistochemical analysis showed the expression of TNF-α and IFN-γ was detected in the neointimal lesion of WT mice, but these cytokines were not detected in the lesion of the corresponding deficient mice. Neointimal formation was significantly reduced after the injury in the DKO mice, compared to that in the WT, TNF-α −/− , and IFN-γ −/− mice (I/M ratio, WT: 2.28±0.17, TNF-α −/− : 2.13±0.20, IFN-γ −/− : 2.37±0.16, DKO: 1.32±0.10, p<0.05, each n=14–17). No significant difference in reendothelialization (CD31 staining) was observed among these groups. Further, vascular smooth muscle cell (α-SMA) and macrophage (F4/80) contents in the neointimal area also did not differ among the groups. The number of proliferating cell nuclear antigen (PCNA) and Ki-67 positive cells in the neointimal lesion was significantly decreased in DKO mice. To determine the contribution of bone marrow cells, we developed 3 types of bone marrow chimeric (BMT Wild→Wild , BMT DKO→Wild , and BMT Wild→DKO ) mice. The neointimal formation in BMT DKO→Wild mice was significantly reduced as compared to that in BMT Wild→Wild (I/M ratio, p<0.05, each n=7) and BMT Wild→DKO mice (p<0.05). These results suggest that the lack of TNF-α and IFN-γ in bone marrow-derived cells synergistically prevents neointimal formation after vascular injury and provide new insights into the mechanisms underlying the restenosis after PCI.